Switch to ChompSMS, works great for me. Had Handcent and the double messages were irritating me.
I was getting duplicate messages and just turned off all the options in handcent settings / receive message settings and its fixed, I get one txt and one notification. doesn't make sense, but its working for me.
Yeah I did. Everything in messaging settings / text messaging is grayed out except the callback number. Everything in handcent settings / notification settings is grayed out except "Notifications (status bar)".